Faecal immunochemical testing (FIT) in primary care: a follow-up service evaluation

Colorectal cancer (CRC) is the fourth most common cancer in the UK. Following National Institute for Health and Care Excellence guidance for faecal immunochemical testing (FIT), we introduced a service for the measurement of faecal haemoglobin (f-Hb) in symptomatic patients. Previously, we evaluated the first 6 months of the service in three local boroughs, here we re-examine the use of FIT, over a similar 6 months in the two successive years.

Patients who had FIT requested in April-September 2020 and 2021 were studied. Results were obtained from the laboratory information systems and matched with the clinical outcomes of those referred via the urgent lower gastrointestinal cancer pathway. Patient demographics, reason for referral, clinical outcome and diagnostic test performance are reported.

In 2020, 4042 samples were analysed and 57 CRC detected. In 2021, 10 508 samples were analysed and 65 CRC detected. Six (4.9%) patients with CRC had f-Hb <10 µg/g, of whom three were anaemic. In 2020, 27.7% of samples were from patients under 50 years; and in 2021, 32.8%. Sensitivity, specificity, positive predictive value and negative predictive value of f-Hb at ≥10 µg/g for CRC were 92.9%, 46.6%, 6.4% and 99.4% in 2020 and 96.9%, 29.9%, 3.2% and 99.8% in 2021.

As currently used in primary care in North East London, specificity of FIT at a cut-off of 10 µg/g is much lower than in published studies and the impact of this on colorectal services needs to be considered.